code: def test_empty_value(monkeypatch):
      monkeypatch.setenv("TEST_ENV_VAR", "")
      assert _EnvironmentVariable("TEST_ENV_VAR", str, None).get() == ""
  
file_path: mlflow/tests/test_environment_variables.py
imports: import os
  import pytest
  from mlflow.environment_variables import _BooleanEnvironmentVariable, _EnvironmentVariable
label_desc: Use image node_id 5 for calling a global function with example usage: test_empty_value(monkeypatch) without return types